Typically, electronic devices packaged beneath a vehicle instrument panel are mounted on a thin substrate (circuit board) enclosed within a plastic box or housing having wiring harnesses running into and out of the device. The box must be mounted to a support structure beneath the instrument panel and supported in an appropriate position, preferably behind the center stack bezel of the instrument panel for providing electronic support to the vehicle temperature control and sound systems, as well as other electronic instrument panel components, such as the antilock brake module, engine control module, air bag module, etc.
This assembly can consume a substantial amount of space beneath the instrument panel. The bulky metal box with bundles of wires extending therefrom has substantial space requirements, and adversely affects packaging design efficiency in the vehicle. Furthermore, the metal box increases manufacturing costs and vehicle weight.
Accordingly, it has been necessary to develop a method and apparatus for integrating assembly of structural and electronic components in a vehicle instrument panel in a manner in which packaging efficiency is improved, and manufacturing time, manufacturing cost, and weight are reduced.
U.S. patent application Ser. No. 08/642,723, now U.S. Pat. No. 5,712,764 assigned to the assignee of the present application, discloses a method of integrating assembly of structural and electronic components by installing circuit trace patterns directly onto structural components of the instrument panel. However, methods of interconnecting such circuits have yet to be developed. It is desirable to provide an interconnection method which incorporates the material of the supporting structure.
Known interconnection techniques have their advantages and disadvantages. For example, soldering will provide an excellent connection, however, it requires the heating of the interface region for attachment and removal of the circuit interconnection. To accomplish this task, the substrate material must be able to withstand elevated temperatures, typically above 183.degree. C. As an alternative to soldering, the circuits may be interconnected using a pin and socket. This technique gives the designer the flexibility to place the interconnection at a desired location. However, using this method, the receptacle is typically soldered in place, and thus raises the same concerns as the direct soldering of the circuits.
In an alternative method, the receptacle may be installed using a compliant press-fit connection. When press-fit or compliant pin technology is used, it requires that the substrate maintain a force on the receptacle for a reliable assembly. Therefore, with a plastic substrate, the material selected must provide higher mechanical strength properties than that of a blow-molded polypropylene (PP), which would be a desirable material for an enclosure structure. The use of a pin to interconnect the electrical circuit will allow the removal of circuits from the substrate. Installation of a circuit with a pin will, however, require an insertion force of several pounds. Due to the compliance of the plastic substrate, the assembly area would have to be supported or buttressed.
Zero insertion force (ZIF) connectors are one possibility for eliminating the force problem referenced above. In zero insertion force connectors, a lever is used to pinch connection members together for electrical interconnection. Low insertion force connectors (LIF) are similar to ZIFs. Both LIFs and ZIFs are mechanically cammed, which requires surface space as well as a planar surface and the addition of a mechanical clamping lever. Such devices typically also include a plastic component which may creep, which results in loss of normal forces over time.
Accordingly, it is desirable to provide a method and apparatus for connecting adjacent circuits which allows for electrical interconnection along nonplanar substrate surfaces, creates an airtight seal to prevent oxygen entry, maintains a large normal force over time, and provides a wiping motion for wiping away contaminants and oxides to facilitate metal-to-metal contact.